Application of PVD W/WN bilayer barrier to aluminum bondpad in wire bonding

Abstract

An aluminum bondpad and method for making the aluminum bondpad is disclosed. In forming aluminum bondpads, a barrier layer is necessary between a copper interconnect layer and the aluminum bondpad layer. Additionally, a gold wiring layer is deposited on the aluminum bondpad layer and annealed at a high temperature to form an aluminum-gold intermetallic compound. Aluminum reacts with tungsten at high temperatures. Therefore, during the annealing, the aluminum will react with the tungsten. By providing a tungsten nitride barrier layer on a tungsten barrier layer, no aluminum-tungsten intermetallic compound will form, even at the high annealing temperatures required to form the aluminum bondpad.

1 . A method for forming an aluminum containing structure, comprising:
 positioning a substrate in a processing chamber;   depositing a tungsten barrier layer over the substrate;   depositing a tungsten nitride barrier layer on the tungsten barrier layer; and   depositing an aluminum layer on the tungsten nitride barrier layer.   
   
   
       2 . The method of  claim 1 , further comprising depositing a copper layer over the substrate before depositing the tungsten barrier layer. 
   
   
       3 . The method of  claim 1 , further comprising depositing a gold wiring layer on the aluminum layer. 
   
   
       4 . The method of  claim 1 , further comprising annealing the structure. 
   
   
       5 . The method of  claim 1 , wherein the structure is an aluminum bondpad structure that comprises a via. 
   
   
       6 . The method of  claim 5 , further comprising annealing the structure to a temperature greater than about 250° C. to reflow the aluminum into a via. 
   
   
       7 . The method of  claim 1 , wherein the depositing is sputtering. 
   
   
       8 . The method of  claim 1 , wherein the aluminum layer comprises up to about 0.5 wt % copper. 
   
   
       9 . The method of  claim 1 , wherein the aluminum layer has a thickness greater than about 1 micron. 
   
   
       10 . The method of  claim 1 , wherein a separate pasting step is not present. 
   
   
       11 . The method of  claim 1 , wherein the tungsten barrier layer and the tungsten nitride barrier layer are formed with a single chamber. 
   
   
       12 . An aluminum structure, comprising:
 a substrate;   a tungsten barrier layer over the substrate;   a tungsten nitride barrier layer on the tungsten barrier layer; and   an aluminum layer on the tungsten nitride barrier layer.   
   
   
       13 . The structure of  claim 12 , further comprising a copper layer between the substrate and the tungsten barrier layer. 
   
   
       14 . The structure of  claim 12 , further comprising a gold layer on the aluminum layer. 
   
   
       15 . The structure of  claim 12 , wherein the aluminum layer comprises up to about 0.5 wt % copper. 
   
   
       16 . The structure of  claim 12 , wherein the aluminum layer has a thickness greater than about 1 micron. 
   
   
       17 . The structure of  claim 12 , wherein no tungsten-aluminum intermetallic compound is present. 
   
   
       18 . The structure of  claim 12 , wherein the structure is an aluminum bondpad structure that contains a via. 
   
   
       19 . The structure of  claim 12 , wherein the tungsten nitride barrier layer is amorphous tungsten nitride. 
   
   
       20 . A method for forming an aluminum bondpad structure, comprising:
 positioning a substrate with a copper layer thereon in a processing chamber;   sputter depositing a tungsten barrier layer on the copper layer;   sputter depositing a tungsten nitride barrier layer on the tungsten barrier layer;   sputter depositing an aluminum layer on the tungsten nitride barrier layer;   depositing a gold layer on the aluminum layer; and   annealing at a temperature of greater than about 250° C.